// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
 ******************************************************************************
 * Copyright (C) 1996-2010, International Business Machines Corporation and   *
 * others. All Rights Reserved.                                               *
 ******************************************************************************
 */

package com.ibm.icu.impl;

import com.ibm.icu.lang.UCharacter;
import com.ibm.icu.text.UTF16;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Arrays;

/**
 * Builder class to manipulate and generate a trie. This is useful for ICU data in primitive types.
 * Provides a compact way to store information that is indexed by Unicode values, such as character
 * properties, types, keyboard values, etc. This is very useful when you have a block of Unicode
 * data that contains significant values while the rest of the Unicode data is unused in the
 * application or when you have a lot of redundance, such as where all 21,000 Han ideographs have
 * the same value. However, lookup is much faster than a hash table. A trie of any primitive data
 * type serves two purposes:
 *
 * <UL>
 *   <LI>Fast access of the indexed values.
 *   <LI>Smaller memory footprint.
 * </UL>
 *
 * This is a direct port from the ICU4C version
 *
 * @author Syn Wee Quek
 */
public class IntTrieBuilder extends TrieBuilder {
    // public constructor ----------------------------------------------

    /** Copy constructor */
    public IntTrieBuilder(IntTrieBuilder table) {
        super(table);
        m_data_ = new int[m_dataCapacity_];
        System.arraycopy(table.m_data_, 0, m_data_, 0, m_dataLength_);
        m_initialValue_ = table.m_initialValue_;
        m_leadUnitValue_ = table.m_leadUnitValue_;
    }

    /**
     * Constructs a build table
     *
     * @param aliasdata data to be filled into table
     * @param maxdatalength maximum data length allowed in table
     * @param initialvalue initial data value
     * @param latin1linear is latin 1 to be linear
     */
    public IntTrieBuilder(
            int aliasdata[],
            int maxdatalength,
            int initialvalue,
            int leadunitvalue,
            boolean latin1linear) {
        super();
        if (maxdatalength < DATA_BLOCK_LENGTH || (latin1linear && maxdatalength < 1024)) {
            throw new IllegalArgumentException("Argument maxdatalength is too small");
        }

        if (aliasdata != null) {
            m_data_ = aliasdata;
        } else {
            m_data_ = new int[maxdatalength];
        }

        // preallocate and reset the first data block (block index 0)
        int j = DATA_BLOCK_LENGTH;

        if (latin1linear) {
            // preallocate and reset the first block (number 0) and Latin-1
            // (U+0000..U+00ff) after that made sure above that
            // maxDataLength >= 1024
            // set indexes to point to consecutive data blocks
            int i = 0;
            do {
                // do this at least for trie->index[0] even if that block is
                // only partly used for Latin-1
                m_index_[i++] = j;
                j += DATA_BLOCK_LENGTH;
            } while (i < (256 >> SHIFT_));
        }

        m_dataLength_ = j;
        // reset the initially allocated blocks to the initial value
        Arrays.fill(m_data_, 0, m_dataLength_, initialvalue);
        m_initialValue_ = initialvalue;
        m_leadUnitValue_ = leadunitvalue;
        m_dataCapacity_ = maxdatalength;
        m_isLatin1Linear_ = latin1linear;
        m_isCompacted_ = false;
    }

    // public methods -------------------------------------------------------

    /*public final void print()
      {
      int i = 0;
      int oldvalue = m_index_[i];
      int count = 0;
      System.out.println("index length " + m_indexLength_
      + " --------------------------");
      while (i < m_indexLength_) {
      if (m_index_[i] != oldvalue) {
      System.out.println("index has " + count + " counts of "
      + Integer.toHexString(oldvalue));
      count = 0;
      oldvalue = m_index_[i];
      }
      count ++;
      i ++;
      }
      System.out.println("index has " + count + " counts of "
      + Integer.toHexString(oldvalue));
      i = 0;
      oldvalue = m_data_[i];
      count = 0;
      System.out.println("data length " + m_dataLength_
      + " --------------------------");
      while (i < m_dataLength_) {
      if (m_data_[i] != oldvalue) {
      if ((oldvalue & 0xf1000000) == 0xf1000000) {
      int temp = oldvalue & 0xffffff;
      temp += 0x320;
      oldvalue = 0xf1000000 | temp;
      }
      if ((oldvalue & 0xf2000000) == 0xf2000000) {
      int temp = oldvalue & 0xffffff;
      temp += 0x14a;
      oldvalue = 0xf2000000 | temp;
      }
      System.out.println("data has " + count + " counts of "
      + Integer.toHexString(oldvalue));
      count = 0;
      oldvalue = m_data_[i];
      }
      count ++;
      i ++;
      }
      if ((oldvalue & 0xf1000000) == 0xf1000000) {
      int temp = oldvalue & 0xffffff;
      temp += 0x320;
      oldvalue = 0xf1000000 | temp;
      }
      if ((oldvalue & 0xf2000000) == 0xf2000000) {
      int temp = oldvalue & 0xffffff;
      temp += 0x14a;
      oldvalue = 0xf2000000 | temp;
      }
      System.out.println("data has " + count + " counts of "
      + Integer.toHexString(oldvalue));
      }
    */
    /**
     * Gets a 32 bit data from the table data
     *
     * @param ch codepoint which data is to be retrieved
     * @return the 32 bit data
     */
    public int getValue(int ch) {
        // valid, uncompacted trie and valid c?
        if (m_isCompacted_ || ch > UCharacter.MAX_VALUE || ch < 0) {
            return 0;
        }

        int block = m_index_[ch >> SHIFT_];
        return m_data_[Math.abs(block) + (ch & MASK_)];
    }

    /**
     * Get a 32 bit data from the table data
     *
     * @param ch code point for which data is to be retrieved.
     * @param inBlockZero Output parameter, inBlockZero[0] returns true if the char maps into block
     *     zero, otherwise false.
     * @return the 32 bit data value.
     */
    public int getValue(int ch, boolean[] inBlockZero) {
        // valid, uncompacted trie and valid c?
        if (m_isCompacted_ || ch > UCharacter.MAX_VALUE || ch < 0) {
            if (inBlockZero != null) {
                inBlockZero[0] = true;
            }
            return 0;
        }

        int block = m_index_[ch >> SHIFT_];
        if (inBlockZero != null) {
            inBlockZero[0] = (block == 0);
        }
        return m_data_[Math.abs(block) + (ch & MASK_)];
    }

    /**
     * Sets a 32 bit data in the table data
     *
     * @param ch codepoint which data is to be set
     * @param value to set
     * @return true if the set is successful, otherwise if the table has been compacted return false
     */
    public boolean setValue(int ch, int value) {
        // valid, uncompacted trie and valid c?
        if (m_isCompacted_ || ch > UCharacter.MAX_VALUE || ch < 0) {
            return false;
        }

        int block = getDataBlock(ch);
        if (block < 0) {
            return false;
        }

        m_data_[block + (ch & MASK_)] = value;
        return true;
    }

    /**
     * Serializes the build table with 32 bit data
     *
     * @param datamanipulate builder raw fold method implementation
     * @param triedatamanipulate result trie fold method
     * @return a new trie
     */
    public IntTrie serialize(
            TrieBuilder.DataManipulate datamanipulate, Trie.DataManipulate triedatamanipulate) {
        if (datamanipulate == null) {
            throw new IllegalArgumentException("Parameters can not be null");
        }
        // fold and compact if necessary, also checks that indexLength is
        // within limits
        if (!m_isCompacted_) {
            // compact once without overlap to improve folding
            compact(false);
            // fold the supplementary part of the index array
            fold(datamanipulate);
            // compact again with overlap for minimum data array length
            compact(true);
            m_isCompacted_ = true;
        }
        // is dataLength within limits?
        if (m_dataLength_ >= MAX_DATA_LENGTH_) {
            throw new ArrayIndexOutOfBoundsException("Data length too small");
        }

        char index[] = new char[m_indexLength_];
        int data[] = new int[m_dataLength_];
        // write the index (stage 1) array and the 32-bit data (stage 2) array
        // write 16-bit index values shifted right by INDEX_SHIFT_
        for (int i = 0; i < m_indexLength_; i++) {
            index[i] = (char) (m_index_[i] >>> INDEX_SHIFT_);
        }
        // write 32-bit data values
        System.arraycopy(m_data_, 0, data, 0, m_dataLength_);

        int options = SHIFT_ | (INDEX_SHIFT_ << OPTIONS_INDEX_SHIFT_);
        options |= OPTIONS_DATA_IS_32_BIT_;
        if (m_isLatin1Linear_) {
            options |= OPTIONS_LATIN1_IS_LINEAR_;
        }
        return new IntTrie(index, data, m_initialValue_, options, triedatamanipulate);
    }

    /**
     * Serializes the build table to an output stream.
     *
     * <p>Compacts the build-time trie after all values are set, and then writes the serialized form
     * onto an output stream.
     *
     * <p>After this, this build-time Trie can only be serialized again and/or closed; no further
     * values can be added.
     *
     * <p>This function is the rough equivalent of utrie_seriaize() in ICU4C.
     *
     * @param os the output stream to which the seriaized trie will be written. If nul, the function
     *     still returns the size of the serialized Trie.
     * @param reduceTo16Bits If true, reduce the data size to 16 bits. The resulting serialized form
     *     can then be used to create a CharTrie.
     * @param datamanipulate builder raw fold method implementation
     * @return the number of bytes written to the output stream.
     */
    public int serialize(
            OutputStream os, boolean reduceTo16Bits, TrieBuilder.DataManipulate datamanipulate)
            throws IOException {
        if (datamanipulate == null) {
            throw new IllegalArgumentException("Parameters can not be null");
        }

        // fold and compact if necessary, also checks that indexLength is
        // within limits
        if (!m_isCompacted_) {
            // compact once without overlap to improve folding
            compact(false);
            // fold the supplementary part of the index array
            fold(datamanipulate);
            // compact again with overlap for minimum data array length
            compact(true);
            m_isCompacted_ = true;
        }

        // is dataLength within limits?
        int length;
        if (reduceTo16Bits) {
            length = m_dataLength_ + m_indexLength_;
        } else {
            length = m_dataLength_;
        }
        if (length >= MAX_DATA_LENGTH_) {
            throw new ArrayIndexOutOfBoundsException("Data length too small");
        }

        //  struct UTrieHeader {
        //      int32_t   signature;
        //      int32_t   options  (a bit field)
        //      int32_t   indexLength
        //      int32_t   dataLength
        length = Trie.HEADER_LENGTH_ + 2 * m_indexLength_;
        if (reduceTo16Bits) {
            length += 2 * m_dataLength_;
        } else {
            length += 4 * m_dataLength_;
        }

        if (os == null) {
            // No output stream.  Just return the length of the serialized Trie, in bytes.
            return length;
        }

        DataOutputStream dos = new DataOutputStream(os);
        dos.writeInt(Trie.HEADER_SIGNATURE_);

        int options =
                Trie.INDEX_STAGE_1_SHIFT_
                        | (Trie.INDEX_STAGE_2_SHIFT_ << Trie.HEADER_OPTIONS_INDEX_SHIFT_);
        if (!reduceTo16Bits) {
            options |= Trie.HEADER_OPTIONS_DATA_IS_32_BIT_;
        }
        if (m_isLatin1Linear_) {
            options |= Trie.HEADER_OPTIONS_LATIN1_IS_LINEAR_MASK_;
        }
        dos.writeInt(options);

        dos.writeInt(m_indexLength_);
        dos.writeInt(m_dataLength_);

        /* write the index (stage 1) array and the 16/32-bit data (stage 2) array */
        if (reduceTo16Bits) {
            /* write 16-bit index values shifted right by UTRIE_INDEX_SHIFT, after adding indexLength */
            for (int i = 0; i < m_indexLength_; i++) {
                int v = (m_index_[i] + m_indexLength_) >>> Trie.INDEX_STAGE_2_SHIFT_;
                dos.writeChar(v);
            }

            /* write 16-bit data values */
            for (int i = 0; i < m_dataLength_; i++) {
                int v = m_data_[i] & 0x0000ffff;
                dos.writeChar(v);
            }
        } else {
            /* write 16-bit index values shifted right by UTRIE_INDEX_SHIFT */
            for (int i = 0; i < m_indexLength_; i++) {
                int v = (m_index_[i]) >>> Trie.INDEX_STAGE_2_SHIFT_;
                dos.writeChar(v);
            }

            /* write 32-bit data values */
            for (int i = 0; i < m_dataLength_; i++) {
                dos.writeInt(m_data_[i]);
            }
        }

        return length;
    }

    /**
     * Set a value in a range of code points [start..limit]. All code points c with start &lt;= c
     * &lt; limit will get the value if overwrite is true or if the old value is 0.
     *
     * @param start the first code point to get the value
     * @param limit one past the last code point to get the value
     * @param value the value
     * @param overwrite flag for whether old non-initial values are to be overwritten
     * @return false if a failure occurred (illegal argument or data array overrun)
     */
    public boolean setRange(int start, int limit, int value, boolean overwrite) {
        // repeat value in [start..limit[
        // mark index values for repeat-data blocks by setting bit 31 of the
        // index values fill around existing values if any, if(overwrite)

        // valid, uncompacted trie and valid indexes?
        if (m_isCompacted_
                || start < UCharacter.MIN_VALUE
                || start > UCharacter.MAX_VALUE
                || limit < UCharacter.MIN_VALUE
                || limit > (UCharacter.MAX_VALUE + 1)
                || start > limit) {
            return false;
        }

        if (start == limit) {
            return true; // nothing to do
        }

        if ((start & MASK_) != 0) {
            // set partial block at [start..following block boundary[
            int block = getDataBlock(start);
            if (block < 0) {
                return false;
            }

            int nextStart = (start + DATA_BLOCK_LENGTH) & ~MASK_;
            if (nextStart <= limit) {
                fillBlock(block, start & MASK_, DATA_BLOCK_LENGTH, value, overwrite);
                start = nextStart;
            } else {
                fillBlock(block, start & MASK_, limit & MASK_, value, overwrite);
                return true;
            }
        }

        // number of positions in the last, partial block
        int rest = limit & MASK_;

        // round down limit to a block boundary
        limit &= ~MASK_;

        // iterate over all-value blocks
        int repeatBlock = 0;
        if (value == m_initialValue_) {
            // repeatBlock = 0; assigned above
        } else {
            repeatBlock = -1;
        }
        while (start < limit) {
            // get index value
            int block = m_index_[start >> SHIFT_];
            if (block > 0) {
                // already allocated, fill in value
                fillBlock(block, 0, DATA_BLOCK_LENGTH, value, overwrite);
            } else if (m_data_[-block] != value && (block == 0 || overwrite)) {
                // set the repeatBlock instead of the current block 0 or range
                // block
                if (repeatBlock >= 0) {
                    m_index_[start >> SHIFT_] = -repeatBlock;
                } else {
                    // create and set and fill the repeatBlock
                    repeatBlock = getDataBlock(start);
                    if (repeatBlock < 0) {
                        return false;
                    }

                    // set the negative block number to indicate that it is a
                    // repeat block
                    m_index_[start >> SHIFT_] = -repeatBlock;
                    fillBlock(repeatBlock, 0, DATA_BLOCK_LENGTH, value, true);
                }
            }

            start += DATA_BLOCK_LENGTH;
        }

        if (rest > 0) {
            // set partial block at [last block boundary..limit[
            int block = getDataBlock(start);
            if (block < 0) {
                return false;
            }
            fillBlock(block, 0, rest, value, overwrite);
        }

        return true;
    }

    // protected data member ------------------------------------------------

    protected int m_data_[];
    protected int m_initialValue_;

    //  private data member ------------------------------------------------

    private int m_leadUnitValue_;

    // private methods ------------------------------------------------------

    private int allocDataBlock() {
        int newBlock = m_dataLength_;
        int newTop = newBlock + DATA_BLOCK_LENGTH;
        if (newTop > m_dataCapacity_) {
            // out of memory in the data array
            return -1;
        }
        m_dataLength_ = newTop;
        return newBlock;
    }

    /**
     * No error checking for illegal arguments.
     *
     * @param ch codepoint to look for
     * @return -1 if no new data block available (out of memory in data array)
     */
    private int getDataBlock(int ch) {
        ch >>= SHIFT_;
        int indexValue = m_index_[ch];
        if (indexValue > 0) {
            return indexValue;
        }

        // allocate a new data block
        int newBlock = allocDataBlock();
        if (newBlock < 0) {
            // out of memory in the data array
            return -1;
        }
        m_index_[ch] = newBlock;

        // copy-on-write for a block from a setRange()
        System.arraycopy(m_data_, Math.abs(indexValue), m_data_, newBlock, DATA_BLOCK_LENGTH << 2);
        return newBlock;
    }

    /**
     * Compact a folded build-time trie. The compaction - removes blocks that are identical with
     * earlier ones - overlaps adjacent blocks as much as possible (if overlap == true) - moves
     * blocks in steps of the data granularity - moves and overlaps blocks that overlap with
     * multiple values in the overlap region
     *
     * <p>It does not - try to move and overlap blocks that are not already adjacent
     *
     * @param overlap flag
     */
    private void compact(boolean overlap) {
        if (m_isCompacted_) {
            return; // nothing left to do
        }

        // compaction
        // initialize the index map with "block is used/unused" flags
        findUnusedBlocks();

        // if Latin-1 is preallocated and linear, then do not compact Latin-1
        // data
        int overlapStart = DATA_BLOCK_LENGTH;
        if (m_isLatin1Linear_ && SHIFT_ <= 8) {
            overlapStart += 256;
        }

        int newStart = DATA_BLOCK_LENGTH;
        int i;
        for (int start = newStart; start < m_dataLength_; ) {
            // start: index of first entry of current block
            // newStart: index where the current block is to be moved
            //           (right after current end of already-compacted data)
            // skip blocks that are not used
            if (m_map_[start >>> SHIFT_] < 0) {
                // advance start to the next block
                start += DATA_BLOCK_LENGTH;
                // leave newStart with the previous block!
                continue;
            }
            // search for an identical block
            if (start >= overlapStart) {
                i =
                        findSameDataBlock(
                                m_data_,
                                newStart,
                                start,
                                overlap ? DATA_GRANULARITY_ : DATA_BLOCK_LENGTH);
                if (i >= 0) {
                    // found an identical block, set the other block's index
                    // value for the current block
                    m_map_[start >>> SHIFT_] = i;
                    // advance start to the next block
                    start += DATA_BLOCK_LENGTH;
                    // leave newStart with the previous block!
                    continue;
                }
            }
            // see if the beginning of this block can be overlapped with the
            // end of the previous block
            if (overlap && start >= overlapStart) {
                /* look for maximum overlap (modulo granularity) with the previous, adjacent block */
                for (i = DATA_BLOCK_LENGTH - DATA_GRANULARITY_;
                        i > 0 && !equal_int(m_data_, newStart - i, start, i);
                        i -= DATA_GRANULARITY_) {}
            } else {
                i = 0;
            }
            if (i > 0) {
                // some overlap
                m_map_[start >>> SHIFT_] = newStart - i;
                // move the non-overlapping indexes to their new positions
                start += i;
                for (i = DATA_BLOCK_LENGTH - i; i > 0; --i) {
                    m_data_[newStart++] = m_data_[start++];
                }
            } else if (newStart < start) {
                // no overlap, just move the indexes to their new positions
                m_map_[start >>> SHIFT_] = newStart;
                for (i = DATA_BLOCK_LENGTH; i > 0; --i) {
                    m_data_[newStart++] = m_data_[start++];
                }
            } else { // no overlap && newStart==start
                m_map_[start >>> SHIFT_] = start;
                newStart += DATA_BLOCK_LENGTH;
                start = newStart;
            }
        }
        // now adjust the index (stage 1) table
        for (i = 0; i < m_indexLength_; ++i) {
            m_index_[i] = m_map_[Math.abs(m_index_[i]) >>> SHIFT_];
        }
        m_dataLength_ = newStart;
    }

    /**
     * Find the same data block
     *
     * @param data array
     * @param dataLength
     * @param otherBlock
     * @param step
     */
    private static final int findSameDataBlock(
            int data[], int dataLength, int otherBlock, int step) {
        // ensure that we do not even partially get past dataLength
        dataLength -= DATA_BLOCK_LENGTH;

        for (int block = 0; block <= dataLength; block += step) {
            if (equal_int(data, block, otherBlock, DATA_BLOCK_LENGTH)) {
                return block;
            }
        }
        return -1;
    }

    /**
     * Fold the normalization data for supplementary code points into a compact area on top of the
     * BMP-part of the trie index, with the lead surrogates indexing this compact area.
     *
     * <p>Duplicate the index values for lead surrogates: From inside the BMP area, where some may
     * be overridden with folded values, to just after the BMP area, where they can be retrieved for
     * code point lookups.
     *
     * @param manipulate fold implementation
     */
    private final void fold(DataManipulate manipulate) {
        int leadIndexes[] = new int[SURROGATE_BLOCK_COUNT_];
        int index[] = m_index_;
        // copy the lead surrogate indexes into a temporary array
        System.arraycopy(index, 0xd800 >> SHIFT_, leadIndexes, 0, SURROGATE_BLOCK_COUNT_);

        // set all values for lead surrogate code *units* to leadUnitValue
        // so that by default runtime lookups will find no data for associated
        // supplementary code points, unless there is data for such code points
        // which will result in a non-zero folding value below that is set for
        // the respective lead units
        // the above saved the indexes for surrogate code *points*
        // fill the indexes with simplified code from utrie_setRange32()
        int block = 0;
        if (m_leadUnitValue_ == m_initialValue_) {
            // leadUnitValue == initialValue, use all-initial-value block
            // block = 0; if block here left empty
        } else {
            // create and fill the repeatBlock
            block = allocDataBlock();
            if (block < 0) {
                // data table overflow
                throw new IllegalStateException("Internal error: Out of memory space");
            }
            fillBlock(block, 0, DATA_BLOCK_LENGTH, m_leadUnitValue_, true);
            // negative block number to indicate that it is a repeat block
            block = -block;
        }
        for (int c = (0xd800 >> SHIFT_); c < (0xdc00 >> SHIFT_); ++c) {
            m_index_[c] = block;
        }

        // Fold significant index values into the area just after the BMP
        // indexes.
        // In case the first lead surrogate has significant data,
        // its index block must be used first (in which case the folding is a
        // no-op).
        // Later all folded index blocks are moved up one to insert the copied
        // lead surrogate indexes.
        int indexLength = BMP_INDEX_LENGTH_;
        // search for any index (stage 1) entries for supplementary code points
        for (int c = 0x10000; c < 0x110000; ) {
            if (index[c >> SHIFT_] != 0) {
                // there is data, treat the full block for a lead surrogate
                c &= ~0x3ff;
                // is there an identical index block?
                block = findSameIndexBlock(index, indexLength, c >> SHIFT_);

                // get a folded value for [c..c+0x400[ and,
                // if different from the value for the lead surrogate code
                // point, set it for the lead surrogate code unit

                int value = manipulate.getFoldedValue(c, block + SURROGATE_BLOCK_COUNT_);
                if (value != getValue(UTF16.getLeadSurrogate(c))) {
                    if (!setValue(UTF16.getLeadSurrogate(c), value)) {
                        // data table overflow
                        throw new ArrayIndexOutOfBoundsException("Data table overflow");
                    }
                    // if we did not find an identical index block...
                    if (block == indexLength) {
                        // move the actual index (stage 1) entries from the
                        // supplementary position to the new one
                        System.arraycopy(
                                index, c >> SHIFT_, index, indexLength, SURROGATE_BLOCK_COUNT_);
                        indexLength += SURROGATE_BLOCK_COUNT_;
                    }
                }
                c += 0x400;
            } else {
                c += DATA_BLOCK_LENGTH;
            }
        }

        // index array overflow?
        // This is to guarantee that a folding offset is of the form
        // UTRIE_BMP_INDEX_LENGTH+n*UTRIE_SURROGATE_BLOCK_COUNT with n=0..1023.
        // If the index is too large, then n>=1024 and more than 10 bits are
        // necessary.
        // In fact, it can only ever become n==1024 with completely unfoldable
        // data and the additional block of duplicated values for lead
        // surrogates.
        if (indexLength >= MAX_INDEX_LENGTH_) {
            throw new ArrayIndexOutOfBoundsException("Index table overflow");
        }
        // make space for the lead surrogate index block and insert it between
        // the BMP indexes and the folded ones
        System.arraycopy(
                index,
                BMP_INDEX_LENGTH_,
                index,
                BMP_INDEX_LENGTH_ + SURROGATE_BLOCK_COUNT_,
                indexLength - BMP_INDEX_LENGTH_);
        System.arraycopy(leadIndexes, 0, index, BMP_INDEX_LENGTH_, SURROGATE_BLOCK_COUNT_);
        indexLength += SURROGATE_BLOCK_COUNT_;
        m_indexLength_ = indexLength;
    }

    /**
     * @internal
     */
    private void fillBlock(int block, int start, int limit, int value, boolean overwrite) {
        limit += block;
        block += start;
        if (overwrite) {
            while (block < limit) {
                m_data_[block++] = value;
            }
        } else {
            while (block < limit) {
                if (m_data_[block] == m_initialValue_) {
                    m_data_[block] = value;
                }
                ++block;
            }
        }
    }
}
